I have it on good authority that parametric types are the way to go. Look at this:
```` #lang typed/racket (struct (α β) point ([x : α] [y : β])) (define-type Point point) (define-type FixedY (Point Real 0)) ```` That's it! On Saturday, January 16, 2021 at 6:26:17 PM UTC+1 [email protected] wrote: > According to https://docs.racket-lang.org/ts-reference/type-ref.html, > `Zero` exists. > > On Sat, Jan 16, 2021 at 8:14 AM [email protected] <[email protected]> wrote: > >> Working in Typed Racket, consider a struct like this: >> >> (struct point >> ([x : Real] >> [y : Real])) >> >> Is there a way to express the type of those points whose y field is, say, >> 0? In other words, I'd like a talk about point structs where x varies >> freely, but y is always 0. Obviously, I can make a function that >> discriminates this subclass, but I'm not sure how to express it as a type. >> I've hunted around in the docs, but I can't quite find what I'm looking for. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Racket Users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/racket-users/ee8bc006-590c-48f6-ac8b-4ef4f88019dfn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/racket-users/ee8bc006-590c-48f6-ac8b-4ef4f88019dfn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/54f032ae-925e-4b15-abe9-caae53e49b83n%40googlegroups.com.
